These investigations are primarily directed to the interaction of toxicants with macromolecules, and secondarily with certain genetic and environmental actions. Although not limited to pesticides the majority of investigations are to that group. Highlights of research findings for this period include: an examination of microsomal proteins utilizing polyacrylamide gel electrophoresis and further characterization of the Type III complex with cytochrome P-450. Type II ligand binding to placental cytochrome P-450 has also been examined as well as further investigations of induction of this cytochrome, including actions initiated prior to birth of rats. Studies with glutathione transferases have included biochemical genetics of housefly resistance and partial purification of this transferase. Structural studies with the purified 315,000 mw horse BChE previously reported have continued and an end chain analysis has revealed one free amino terminal residue and probably one other residue. Experiments with a number of insecticides and herbicides are being directed to effects on phosphorylation in mammals. A comprehensive survey of the problem of reentry of agricultural workers into fields previously treated with OP insecticides has shown that three main groups of workers appear to be at slight risk. Genetic studies have included electrophoretic examination of ovarian proteins following treatment by three folic acid antagonists. Activities on the genetic action of herbicides, fungicides, and certain chlorinated compounds are continuing in order to determine subtle genetic effects on classic organisms.